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Covariance Control for a class of Stochastic Discrete-time Linear Systems using the S-Variable Approach
No full textThis paper deals with the problem of covariance control for a class of linear stochastic discrete-time systems in the Stochastic Model Predictive Control (SMPC) framework. The considered systems are affected by independent and identically distributed (i.i.d.) additive and parametric stochastic uncertainties (potentially unbounded), in addition to polytopic deterministic uncertainties bounding the mean of the state and input parameters. The control design conditions presented in this paper are formulated as Linear Matrix Inequalities (LMIs), using the S-variable approach in order to reduce the potential conservatism. These conditions are derived using a deterministic exact characterization of the covariance dynamics, the latter involves bilinear terms in the control gain. A technique to linearize such dynamics is presented, it results in a descriptor representation allowing to derive sufficient conditions for covariance control design. The derived condition is firstly compared to a known necessary and sufficient stability condition for systems without deterministic uncertainties and additive stochastic noise, although more conservative, it turns out to be more numerically tractable. Then, the same condition is used to design controllers that are robust to both deterministic and stochastic uncertainties. Several numerical examples are presented for comparison and illustration
Multiplexed Bio‐detection on an Interferometric Optical Waveguide Assembly
No full textInternational audienceMultiplexed remote bio‐detection is demonstrated through an optical waveguide assembly coated with interferometric layers. Image conduits (IC)s, composed of 3012 individual cores, are coated with interferometric layers of tantalum pentoxide (Ta 2 O 5 ) and silica (SiO 2 ) to transform each core into a sensitive sensor. The spectral response of the IC as a function of refractive index (RI) changes is obtained and compared with the simulated one. The experimental sensitivities and resolutions of individual cores of the waveguide are assessed in remote detection mode by imaging through the optical assembly. For 75% of the cores, a sensitivity better than 510%. RIU −1 (RI Unit) is obtained, corresponding to a resolution better than 7 × 10 −4 RIU. Furthermore, the coated face of IC is functionalized with two localized arrays of hundred‐micrometer droplets containing two different oligonucleotide (ODN) probes using a polymeric 3D‐printed microcantilever. Hybridization of complementary ODN strands is detected for one of the probes, the second being a negative control. Interaction kinetics are monitored in functionalized areas by grouping several cores or on individual cores. Thus, multiplexed bio‐detection on the surface of an interferometric waveguide is demonstrated for the first time paving the way for applications in multiplex in situ biosensing, and, ultimately, in vivo endoscopic diagnosis
Humanoid Robotics: Integrating Cognitive and Physical Abilities for Human-Centered Environments [From the Guest Editors]
No full textInternational audienc
Cell cycle phases, their effect on cell mechanical properties and the impact on Candida-host cell interaction
No full textInternational audienceCell mechanics is essential in many biological phenomena such as cell division, and migration. Further, cell mechanobiological measurements can distinguish between healthy and diseases cells, thus, investigations of cell mechanics have led to the development of tools to study the elasticity and the viscosity of cells. Cell mechanics can be affected by factors such as cell morphology, and cytoskeletal remodelling and cell intrinsic factors and these are important in understanding disease progression. Here we use an atomic force microscopy (AFM)-microrheology with a colloidal probe for a dynamic mechanical analysis of host cell elasticity and viscosity at 6 frequencies ranging from 1 Hz to 200 Hz. Epithelial cells exhibit a more "liquid-like" behavior as the frequency increases, whereas cancerous cells transition into this viscous, fluid-like state at lower frequencies (48 and 63 Hz) compared to normal cells (92 Hz).Cell mechanical measurements inherently exhibit heterogeneity due to physical factors such as cell shape and the position of the probe on the cell surface. In addition to this physical variability, biological parameters -notably the cell cycle phases -also contribute to mechanical heterogeneity. In this study, we specifically investigated the influence of cell cycle phases on cell mechanical properties. Using chemically synchronized normal and cancerous cells in different phases of the cell cycle, shows that the actin cytoskeleton undergoes rapid reorganization as the cell cycle progresses.Results show that as actin becomes disorganized the elastic moduli decreases, the loss tangent is larger coupled with a lower phase shift frequency. Cells in the G1 and S phase had the lowest elastic moduli (G') meaning they were softer than cells in G2/M phase.During disease onset the pathogen adheres and invades the host, a process which leads to cytoskeleton arrangement and thus, changes in cell elasticity and thus, to understand the impact of the cell cycle on host invasion we probed the interaction of C. albicans with HeLa, HCT 116 and HaCaT cells using AFM in single cell force spectroscopy mode. There was a significant increase in force of interaction during the S phase which could be attributed to the disorganized cytoskeleton. This shows the importance of cytoskeletal organization and cell cycle phase in cell mechanical properties and pathogen-host interaction.</p
A Novel Dual-Key Authentication via Wireless Power Transfer for Secure SWIPT-Based IoT Systems
No full textInternational audienceThis article presents a novel mechanism to enhance security of battery-free, wirelessly powered IoT devices, in line with the Simultaneous Wireless Information and Power Transfer paradigm. The proposed authentication method uses a combination of public and private keys implemented on the Wireless Power Transfer link enabled by the backscattering of the power wave. This mechanism operates independently of the wireless communication protocol, ensuring a universal compatibility across IoT devices without increasing their energy consumption. This approach has been implemented and tested on a battery-free wireless Sensing Node within a LoRaWAN-based Wireless Sensor Network. The power wave is modulated with a digital Public Key by the power source, and a digital Private Key is generated by the Backscattering Rectifier of the battery-free wireless Sensing Node to guarantee a dynamic authentication frame to prevent it from being copied and reused in replay attacks
Designing asymptotically optimal policies for continuous-time weakly coupled MDPs
No full textInternational audienceWe study the continuous-time Weakly Coupled Markov Decision Process (WCMDP), a class of decision problems involving multiple interacting Markov processes (or "arms") subject to shared resource constraints. We present a general framework for policy design using a combination of an underlying Markov process and a sequence of mappings. Our main theoretical result establishes sufficient conditions on the Markov process and mapping defining the policy, such that it is asymptotically optimal as the number of arms grows.We construct both deterministic and randomized policies based on a solution to a linear program (LP). These policies initially assign actions to arms-either proportionally (deterministic) or randomly-based on conditional measures derived from the LP. As this initial allocation may violate feasibility constraints, we introduce a mapping to enforce the resource constraints are satisfied. Finally, we numerically evaluate and compare the performance of our proposed policies, both deterministic and randomized, under different choices of mappings.</p
Regional stability conditions for recurrent neural network-based control systems
No full textInternational audienceIn this paper we propose novel global and regional stability analysis conditions based on linear matrix inequalities for a general class of recurrent neural networks. These conditions can be also used for state-feedback control design and a suitable optimization problem enforcing norm minimization properties is defined. The theoretical results are corroborated by numerical simulations, showing the advantages and limitations of the methods presented herein
The ARMAGNHAC database: A Ratio-based Molecular Analyzer and Generator of Numerous Hydrogenated Amorphous Carbons
No full textInternational audienceHydrogenated amorphous carbons (HACs) are complex disordered forms of carbons that are of interest in various scientific fields, such as the study of air pollution from soot particles and astrochemistry. A new stochastic, structurally-guided algorithm, is presented for large-scale generation of atomistic models of HACs. It consists of a two-step procedure: (i) the randomized generation of 2D structures, using the SMILES (Simplified Molecular Input Line Entry System) description, respecting user predefined chemical constraints; (ii) the subsequent generation of 3D structures, making use of a stochastic sampling algorithm combined with local optimizations at the DFTB (density functional based tight binding) level. The method was used to generate the ARMAGNHAC database (website: https://armagnhac.laas.fr/) which provides structural (cartesian coordinates, functional group ratios, Hill-Wheeler parameters and aromaticity descriptors), energetic (HOMO-LUMO gap, ionization energy and electronic affinity) and spectroscopic properties of 4366 HACs. Correlation plots between these descriptors can be generated on the website, as well as IR spectra, possibly including their evolution as a function of a given property. Several illustrations are given, such as the dependence of the ionization potentials and electronic affinities on the size of the largest aromatic island of the HACs. The database (structures and properties) can be downloaded by the users. This work paves the way for future studie
Méthodologie innovante pour la caractérisation dynamique, reproductible et sans parasite de composants p-GaN HEMTs ; mise en évidence d'effets exclusivement dynamiques
No full textNational audienceDes p-GaN HEMTs à grille schottky sont étudiés en fonctionnement dynamique, sans parasites, grâce à un environnement de test 50 Ohms spécialement conçu. Des phénomènes dynamiques exclusifs sont mis en évidence, notamment une phase de transition des énergies de commutation ; et une montée drastique du Ron, allant jusqu'à cinquante fois sa valeur nominale en présence de surtensions transitoires de grille. Ce phénomène est structurel, causé par la grille schottky. Contrairement au comportement observé en mesures quasi-statiques, les résultats sont reproductibles sans préconditionnement